Fluorides were added to the water supply of a school in Seagrove, North Carolina. The concentration of fluoride used was 7 times higher than the level considered optimal for community water fluoridation in the geopgraphic area. Children attending the Seagrove school live in an area where the various sources of well water contain negligible levels of fluoride. Baseline dental examinations for dental caries were made prior to the installation of fluoridation equipment. Follow-up examinations were conducted after four, eight, and twelve years to determine the extent of caries protection as increasingly arger segments of the study population become continuously exposed to fluoridated water at school since entering the first grade. Results of the four-and eight-year examinations on full beneficiaries of the procedure showed decreases in caries prevalence of 30 and 40%, respectively, compared with baseline findings. On the eight-year examinations, an assessment of the prevalence of dental fluorosis showed that no children had any definite signs of the condition